With recent prevalence of digital cameras and camera-mounted mobile phones, imaging elements such as CCD imaging elements and C-MOS imaging elements have been increasingly demanded. In order to meet a demand for higher image quality, the imaging elements tend to have a drastically increased number of pixels. Particularly, with prevalence of digital single lens reflex cameras, the imaging elements tend to have an increased size. In recent years, light emitting elements have become capable of emitting a great amount of light or emitting white light with the use of a fluorescent material in combination. Therefore, light emitting diodes employing the light emitting elements are widely used as flashes for the camera-mounted mobile phones.
In order to ensure that the imaging elements, the light emitting elements and like semiconductor elements sufficiently exhibit their capabilities for higher output, there is an increasing demand for a semiconductor element mount employing an insulative member composed of a ceramic material such as AlN having a higher heat dissipating capability. For example, the insulative member of the semiconductor element mount has opposite surfaces which respectively serve as a main surface for mounting a semiconductor element and an external connection surface for connection to a second component. The semiconductor element mount includes a plurality of electrode layers provided on the main surface for mounting the semiconductor element, a plurality of electrode layers provided on the external connection surface for the connection to the second component, and electrically conductive layers or via-conductors respectively provided in a plurality of through-holes extending through the insulative member for individually connecting the electrode layers provided on the main surface to the electrode layers provided on the external connection surface.
Conventionally, the semiconductor element mount is typically produced by a so-called co-firing method employing a ceramic green sheet as a precursor material for the insulative member (see, for example, the following Patent Publications 1 and 2). That is, the ceramic green sheet is formed as having a plane shape corresponding to the outer shape of the insulative member, and through-holes are formed at predetermined positions in the ceramic green sheet. In the case of the via-conductors, an electrically conductive paste to be co-fired with the ceramic green sheet for the formation of the via-conductors is filled in the through-holes. Then, the ceramic green sheet and the electrically conductive paste are simultaneously fired. Thus, the semiconductor element mount is produced.
Further, an electrically conductive paste is, for example, printed or applied in predetermined plane shapes corresponding to the shapes of the electrode layers on opposite surfaces of the ceramic green sheet of a predetermined plane shape later serving as the main surface and the external connection surface of the insulative member, and the electrically conductive paste and the ceramic green sheet are simultaneously fired to form underlying metal layers. Then, metal layers are formed on the underlying metal layers by plating, whereby the electrode layers are formed on the main surface and the external connection surface.    Patent Publication 1: Japanese Unexamined Patent Publication JP, 11-135906, A (1999)    Patent Publication 2: Japanese Unexamined Patent Publication JP, 2002-232017, A